Heat pumps & solar panels: the expert guide

If you like the idea of solar panels, chances are you’ll be thinking of adding a heat pump too – after all, you can run it on the electricity you generate with your panels.

And with Sunsave Plus offering solar panels for no upfront cost and government grants reducing the price of heat pumps, now is an excellent time to make the switch.

In this guide, we’ll explain how using a heat pump with solar panels works, how many panels you’ll need, and which properties are suitable.

If you would like to see the savings you could get from a solar & battery system, answer a few questions below and we’ll provide an estimate.

How does it work?

Like a gas boiler, your heat pump will stay on at all times, but will only run – and use substantial amounts of electricity – when it’s needed.

So whenever your property drops below the preferred temperature you’ve set – either according to your thermostat or thermostatic radiator valves – your heat pump will start running.

When this happens during the day, your solar panels will at least partly power your heat pump.

The solar electricity your system produces is sent to power as many electric appliances running in your home as possible. There’s no hierarchy of needs or way of telling which devices receive this green electricity.

So if your solar panels produce 0.7kWh of electricity over an hour, and you use 0.7kWh or less in that hour, your heat pump’s energy consumption will be 100% solar over that time.

If you consume 1kWh in that hour, your entire home’s electricity usage will be 70% solar – including your heat pump.

Adding a solar battery to your system will enable you to run your heat pump – and other home appliances – with solar electricity more of the time, which will cut your energy bills further.

There’s no such thing as a 'solar heat pump' that’s more compatible with solar panels than other models, since all heat pumps work well with solar panels.

This is for the best, since your heat pump will also almost certainly need to use grid electricity at various times.

Can solar panels fully power a heat pump?

It's unlikely that solar panels will fully power your heat pump, unless you get an extraordinarily large system.

This is mostly down to heating needs being highest in winter, when solar panels usually produce less electricity.

A 2024 study by the Fraunhofer Institute for Solar Energy Systems analysed the impact of a solar & battery system on a home with a heat pump.

It found that the 12.3 kilowatt-peak (kWp) solar panel system and 11.7kWh battery supplied 36.2% of the electricity necessary to run a 13.9kW ground source heat pump for the 256m² house.

This 36.2% figure is also known as the 'solar fraction', which refers to the percentage of total electricity needed for the heat pump that the solar & battery system supplies.

Of the 5,064kWh of electricity the heat pump consumed, 17.8% came directly from the solar panels, and 18.4% was sourced from the battery. The other 63.8% was grid electricity.

Solar vs grid: a heat pump case study

This is an unusually large solar & battery system, supplying electricity to a big heat pump – but since it was all sized up together, the solar fraction should be consistent with a more regular setup.

It should therefore give you a good idea of what to expect if you combine a heat pump with a solar & battery system, though it's still just one example.

Your solar fraction could be much higher, depending on multiple factors.

These include the size of your solar panel system, battery, and heat pump, and whether or not you run your heat pump's hot water heating and disinfection cycle during daylight hours.

We'll explain the pros and cons of doing this further down.

Air source vs ground source heat pumps

Air source heat pumps use the warmth present in the air as fuel, whereas ground source heat pumps absorb geothermal warmth, using underground pipes.

The complex, disruptive nature of a ground source heat pump installation – which involves either laying 30-50 metres of pipe or drilling boreholes in your garden – makes it the more expensive option.

But in terms of how solar panel systems power them, the two types of heat pumps are identical. As well as natural warmth, they require electricity to function, which solar panels supply.

Ground source heat pumps are usually more efficient across the year, since it's warmer below ground than above it, on average.

They also tend to be more powerful, though this has more to do with the households that have the space and money to get one, rather than being an inherent trait.

This all means ground source heat pumps will make slightly better use of the solar electricity you provide them with, and will generally need more of it.

It's always true that you'll save and earn more with a larger solar panel system, but this fact is especially crucial when you're boosting your electricity usage with a ground source heat pump.

A typical three-bedroom home will need a 8.2kWp system to run a heat pump for most of the year, which you can do by getting 19 solar panels with 430-watt peak ratings.

However, a smaller system will still save you a significant amount on your electricity bills.

A heat pump with an average efficiency rating of around 350% – that is, one that produces three and a half times as much energy as the electricity it takes in – will need around 3,200kWh (kilowatt-hours) per year to heat the average three-bedroom household.

Since the same household needs 3,400kWh of electricity per year to power its other appliances, it requires a total of 6,600kWh, which in the UK can typically be achieved with 19 panels.

Getting a system this size will cut your heating bill significantly, especially if you also get a storage battery.

This will ensure that even after the sun goes down, you can use solar electricity to heat your home – shrinking your bills further.

Winter vs summer

No realistic domestic setup will be fully sufficient in winter, when solar panels generate less electricity – around 11% of their annual output – right as the thermometer drops and heating usage rises.

As a result, your self-consumption rate should rise. In the study mentioned above, scientists found the household used 94%-100% of its solar electricity in winter, because of this imbalance between supply and demand.

In this situation, with the household's solar fraction plummeting to a high of 26% just as the heat pump requires 63% of its annual usage, the grid will smoothly plug the gap.

During the summer however, your panels are very likely to produce excess electricity, which you can sell to the grid via a solar export tariff.

Due to this overabundance of solar electricity, self-consumption for the home in the study fell below 50% between May and August, hitting a low of 25% in July. The rest can be sold to the grid.

The study also discovered that the heat pump's solar fraction increased above 90% in summer, as the household only relied on it for hot water.

So even though you’ll need to rely on the grid to provide some electricity for your heat pump in winter, you can still save and earn hundreds of pounds per year with a solar & battery system.

How much does a heat pump with solar panels cost?

A heat pump with a solar & battery system that can power your home’s electricity and heating for most of the year would usually cost the average household £28,000 – but you can reduce this to £5,000 upfront with the Boiler Upgrade Scheme and Sunsave Plus.

Buying a heat pump and getting it installed typically costs around £12,500, according to the Microgeneration Certification Scheme (MCS), but the government’s Boiler Upgrade Scheme can cut this amount to £5,000.

If you get an 8.2kWp solar panel system with a 5.2kWh battery – which should ensure most of the electricity you use comes from your solar panels – this would usually cost you around £15,500. To learn more, check out our guide to solar panel costs and solar battery costs.

However, if you sign up to Sunsave Plus, you can get this system with no upfront cost.

You’ll also receive the Sunsave Guarantee, which includes 20 years of 24/7 monitoring and maintenance, free battery and inverter replacements, and downtime cover. Your system will also be insured by Aviva.

Is your home suitable for a heat pump and solar panels?

Most homes in the UK are suitable for a heat pump and solar panels.

Heat pumps can be installed in all property types – from flats to detached houses – and in homes from any architectural era, according to the government-funded Electrification of Heat project.

That means your property’s suitability will instead come down to whether you have a good level of insulation, and enough space for the different components. You’ll need room outside for the external unit, and space inside to fit a hot water cylinder.

Ideally, you’d also have underfloor heating or large radiators, but it’s not essential.

To be suitable for solar panels, you’ll just need to own a suitable roof that’s at least mostly unshaded, faces south, east, or west (although north-east and north-west will sometimes be sufficient), and can support the weight of panels – which most can.

The best import & export tariffs for a heat pump with solar

The best import and export tariffs for a solar home with a heat pump are currently provided by Octopus and E.ON.

If you choose Octopus's 15p per kWh Outgoing Fixed export rate, you should sign up for Cosy Octopus, which offers three daily off-peak periods when importing is 51% cheaper than the standard variable rate.

Households that go with E.ON can benefit from Next Export Premium v2, which pays 21p per kWh but is only available if you install with E.ON – or Next Export Exclusive, a 16.5p per kWh rate for the supplier's electricity customers.

In either case, you should also sign up for E.ON Next Drive, which enables you to import electricity for 6.7p per kWh from 12am to 7am.

Homes with a large battery will generally benefit more from picking E.ON, since its off-peak import rate is considerably lower.

If you do select one of these import tariffs, you should mark its off-peak times by charging your battery, using some of your highest-consuming machines (e.g. your washing machine), and scheduling your heat pump's hot water heating and disinfection cycle.

Another option is to charge your battery on off-peak electricity, use this supply to power your home and heat pump, then export 100% of your solar-generated electricity.

In some situations, this may be more profitable – though of course, you still won’t be able to power your heat pump with a battery alone.

To read our full guide to import and export rates, check out our guide to the best solar export tariffs.

At Sunsave, we’ll consider your individual circumstances before making a recommendation.

Next steps

The best way to run a heat pump is with free, green electricity produced by your own solar panels.

You can cut your energy bills by hundreds of pounds per year, and take advantage of tariffs that reward you for using your heat pump and solar electricity in certain ways.

With government grants like the Boiler Upgrade Scheme making heat pumps affordable and Sunsave Plus providing a solar & battery system at no upfront cost, this is a great time to jump on board.

If you’re interested in how much you could save with a solar & battery system, just answer a few quick questions below and we'll generate an estimate for you.

Heat pumps with solar panels: FAQs